Snakes
of the
Sea
words/pictures
WALT DEAS
Scottish diving legend Walt Deas files regular reports for SCOTTISH
DIVER from his home in Australia. In this edition the underwater
photographer and marine life expert provides a colourful account
of an unusual type of marine life - sea snakes ...
SEA SNAKES are cold-blooded
reptiles consisting of some 70 species,
and are found primarily in warm
tropical waters of South Asia, Australia, and throughout the Indo-Pacific.
One species, the pelagic Yellow-Bellied
sea snake Pelamis platurus ranges
across the Pacific to the western coasts
of Central and South America and
south to New Zealand and the Cape of
Good Hope and Madagascar.
Pelamis platurus can sometimes be
found swarming in the hundreds in
the open ocean. During a trip between
two reefs in my 21ft powerboat in the
1980s I saw what looked like a number
of tree branches sticking out of the sea.
I headed over and much to my
consternation I found that it was a
large number of sea snakes that
bobbed up and down in the slight
Images this page: top - A close-up of Stoke’s
Sea Snake; above - Olive Sea Snake
(Aipysurus laevis. Common in reefs in Papua
New Guinea, Australia & the Coral Sea & left
- extracting venom from a Olive Sea Snake
We recently reviewed Walt and Jean
Deas latest book Coral Reefs Natures
Wonders. We are pleased to say the
book now has a European distributor.
The book is available at £22.50 from
www.eurospanonline.com or
[email protected].
Page 22
swell. Not knowing much about sea
snakes in those days I decided to leave
when a few suddenly came over to the
boat.
Sea snakes have specialised flattened
tails for swimming and have valves
over their nostrils which are closed
underwater. Sea snakes belong to a
group related to cobras and some are
known to have venom 10 times as
strong as a rattlesnake’s. It is composed of powerful neurotoxins that
have an effect on the nervous system
and sometimes myotoxins that affect
skeletal muscles.
Eels are sometimes confused with
sea snakes; however, no sea snake has
fins or gill openings, and none have
smooth skin without scales. They feed
on small fish and are preyed upon by
sea birds, sharks, larger fish and
humans. Their potent venom
quickly immobilises their
prey.
There are 31 species of sea
snake in northern Australian
waters alone; all are potentially dangerous to humans.
They are generally mild
mannered reptiles, although
both individual and species
variation exists with respect
to this trait. Usually in open
water they either seek to
escape or remain indifferent
to swimmers. Stranded on
Dubois’ Sea Snake, Aipysurus duboisii resting on the
bottom. Aggressive individuals have been encountered.
beaches, most species are totally
helpless. Bites from sea snakes occur
when they are kicked or trodden upon
in shallow water or when they are
being removed from nets, traps and
other fishing gear.
Some can be aggressive during the
mating season and the sea snake is
usually very curious, they can become
fascinated by drawn out items such as
your high pressure or regulator hoses.
Provoked snakes can become very
aggressive and persistent, requiring
repeated kicks from fins to ward them
off.
On a trip out to Saumarez and Kenn
Reef in the Coral Sea, sea snakes were
very much in evidence and some were
very aggressive. One scuba diver, the
editor of a dive magazine was chased
from 24 metres to the surface and then
across the surface before reaching the
safety of the charter vessel. A tale that
never appeared in the magazine.
At odd times while absorbed in
taking a photograph one would
suddenly find a sea snake wrapped
around a leg or arm - a most heartdisturbing event. Others would zoom
up from the bottom, and dodge every
attempt to keep them at bay. However
David Ross with a large sea snake that wrapped itself
around his arm. Saumarez Reef, depth 30 metres.
the majority were docile.
Regardless of the reputed docility of
these creatures, it should be kept in
mind that the venom is extremely
potent and could prove fatal.
Persistent myths about sea snakes
include the mistaken idea that they
can’t bite very effectively. The truth is
that their short fangs are adequate to
penetrate a wet suit. They can open
their mouths to bite an arm as demonstrated to me one day when one bit
into a 90cm round section of wood
wrapped in an old wet suit arm.
Remember that they can swallow a
fish that is more than twice the
diameter of their neck. They can
dislocate their jaws in the same
manner as terrestrial snakes.
The bite is usually felt and small
marks are visible; pain and swelling
from the site can be minimal. If
symptoms do not occur within six to
eight hours, then significant poisoning
has not occurred. Symptoms can
develop slowly, ‘aching’ and ‘stiffness’.
Then generalised paralysis. Pulse
becomes weak and irregular; thirst,
nausea, difficulty in speaking and
vomiting develop. The symptoms
become more intense; the skin be-
comes cold, blurred vision, drowsiness
and finally respiratory paralysis.
Only a small proportion of bites are
fatal. There is one thing - if recovery
occurs, it’s rapid and complete!
(more images on Page 26)
© Walter Deas. 2005.
Ben Cropp with Stoke’s Sea Snake (Astrotia
stokesii). Note the bite out of its tale. This
sea snake was one of a number captured for
scientific study and released.
Page 23
Snakes of
the Sea
A juvenile Stoke’s sea snake heads to the surface for a breath of air
(Lady Elliot Island)
Dr. Harold Heatwole demonstrates the fang of an olive sea snake.
Walt Deas videos a juvenile Stoke’s sea snake at Lady Elliot Island
(photo - Clint Hemsall)
Page 24